Water is commonly employed in coal crushing and washing operations as a vehicle and to collect and suppress fines. However, water is desirably removed from cleaned ores and coal prior to delivery of the product to a user for two important reasons. First, surface moisture much in excess of about five percent can result in serious freezing of ore in railroad cars when shipment is made in sub-freezing weather. Second, and more importantly, in the case of coal any included moisture acts as a B.T.U. thief, the fuel value of clean coal being an inverse function of its moisture content. Likewise in the further processing of ores, moisture must often be removed.
In the past, partial dewatering of ore slurries has been accomplished by such procedures as filtration and centrifugation, sometimes followed by thermal drying to a target moisture level. In addition, dewatering aids have been utilized heretofore in instances where the cost effectiveness of the chemical additives exceeded the incremental equipment charges and related energy costs. One commonly employed dewatering aid has been a surface active chemical species known generically as sodium dialkylsulfosuccinate (see for example U.S. Pat. No. 4,210,531); but this material is often prohibitively expensive in its application, usually exhibits a very significant foaming tendency, and therefore has limited utility.
My commonly assigned related application, Ser. No. 364,463 filed Apr. 1, 1982, now U.S. Pat. No. 4,410,431, hereinafter incorporated by reference, discloses and claims the use of certain non-ionic surfactants useful as de-watering aids which have been combined with Tall Oil Fatty Acids so as to solubilize higher concentrations of the non-ionic surfactant. It was discovered, quite surprisingly in that application, that the two ingredients act synergistically in the dewatering of mineral concentrates.